The invention relates to reciprocating internal combustion engines fueled by turbine fuels, and more particularly of the type that operates on a combined stratified, spark-assisted compression ignition and torch-assisted compression ignition processes utilized with aviation turbine fuels.
Competition in the world for fossil fuels among various transportation segments will continue to grow and those fuels that are manufactured in relatively low quantities are becoming more expensive and vulnerable to critical shortages and environmental demands. Among aviation fuels, gasolines have proven to be the most vulnerable and the additional environmental constraints such as total elimination of lead as an anti-detonant additive are further threatening the future availability of high octane aviation gas. Automotive gasolines may provide a practical alternative to the low performance range of piston aircraft engines. However, high performance and high altitude piston aircraft engines must continue to depend upon high octane aviation gasolines, or an alternative fuel. There are large worldwide supplies of turbine fuels due to airline and military requirements which will be maintained in the foreseeable future. Such fuels offer plentiful supplies with existing distribution systems and are devoid of liability burdens associated with automotive gasolines used in aircraft.
Stratified charge engines have been in existence for over 50 years, as exemplified by the Ricardo Pat. No. 2,191,042. These engines in isolated cases have successfuly operated with turbine fuels, however, they have been used in ground transportation applications. Both stratified and diesel turbine fuel adaptations of the past represent low specific output engines with limited regard for economic considerations and their principal objectives being to meet particular emission standards and multi-fuel capabilities. All of the prior developments in these areas have failed to produce a light and efficient high specific output engine capable of operating on turbine fuels.
A number of prior art patents use a pilot fuel spray which is ignited by an electrical spark or surface heated element to establish a flame or stream of hot gases which in turn is used to ignite a main fuel charge such as typified by Hoffman, U.S. Pat. No. 2,902,011 and Loyd, U.S. Pat. No. 4,414,940.
The concept of shaping the piston crown to promote swirl as the piston approaches top dead center is generally taught in the patent to Yamakawa, U.S. Pat. No. 4,166,436, and applicant's recently granted U.S. Pat. No. 4,594,976.